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Dear Bob, Steve and others
I've now got the 802.3af D4.2 spec, as well as
EN60950-1:2001 and I've done my best to understand them. (Note I have EN60950,
not IEC60950), as far as they apply to the design of a PD. Can you check
that I've got it right?
1 802.3af clause 33.4.1 says
separation in in accordance with IEC60950 clause 6.2, which in turn calls for
"adequate separation", without defining this. Compliance is tested by performing
tests specified in 6.2.2 and EXPLICITLY STATES that the "... requirements of
2.10 regarding the dimensions and construction of CLEARANCE, CREEPAGE DISTANCE
and solid insulation do not apply...". Is this really saying that all I
have to do is pass the electric strength tests, and not comply with any creepage
and clearance specs?
2 If that is the case, there
still must be some useful guidelines I should apply to creepage, clearance,
insulation etc. Any pointers?
3 I note that 802.3af clause
33.4.1 calls for either 1500Vrms steady-state, or 1500V pulses. The EN60950 spec
calls for higher voltages for the impulse tests that the steady-state tests, and
this seems to be the policy of IEEE802.3 (in 14.3.1.1, for example). Is it
really the intention of the 802.3af spec that the steady-state and pulsed
voltages should be the same? (Just checking!)
Many thanks.
Regards -
Charles Palmer Technical Director, DSP Design Ltd
email: charles@xxxxxxxxxxxxx 7 Tapton Park Innovation Centre, Brimington Rd, Chesterfield S41 0TZ, UK ph: +44 (0) 1246 545 918 |